these lines are begging me to cross
by tonberrys-and-kuchikopi
Summary: The Mark of Lord Voldemort's chosen brings with it certain responsibilities, and while other students relax and enjoy the 1978 Christmas holidays, Regulus and Barty are taught the three Unforgivable Curses with Bellatrix as their guide. (The Cause would pause for no one, student or not.) Part of the Renascentia-verse.


Note: This one-shot is written by "tonberrys."

Title is taken from "These Walls" by Trapt.

As a warning, there is some animal torture popping up in here again. :( Not terribly graphic, but somewhat prominent, given the subject matter of this one.

* * *

A brush of frost framed the windows at the Lestrange Manor. The Christmas holidays were upon them, heralding the approaching end of his time at Hogwarts School of Witchcraft and Wizardry, but there would be no time to rest, this Christmas.

"Tonight, we take your training to the next level." Bellatrix's voice was crisp and clean as she clasped her hand behind her back, eyes flicking between her two students as they stood in rapt attention. "Three curses to represent the pillars of our power: Control, torment, elimination." Her eyes locked with Regulus's then, and he felt the weight of her words, careful to keep his face a stony mask of neutrality despite the subtle prick of nervousness. Cooly, Bellatrix continued, "I assume I do not need to waste time telling either of you about these curses, the power behind them, or the consequences for getting caught, so we will move immediately to the practical application. We have only two weeks before you must return to school, so I expect you to practice diligently until you are proficient."

Regulus mirrored her stance, clasping his hands behind his back with a straightened posture, even as his fingers twisted nervously in the sleeve of his cloak. The previous two summers had been ripe with dark magic, progressing through a more extensive and terrible arsenal of spells than he thought he could possibly need, even once he was finished with his schooling next year.

This Christmas holiday curriculum was a steep climb above them all. With a Mark on his arm and the Trace lifted, the time to learn the Unforgivables had apparently come, and there would be no side-stepping them with Bellatrix as a mentor, no matter how blatantly illegal they might be.

Sparing a glance to the side, he saw the subtle glow of eagerness lifting Barty's expression. His friend had proven to have a better stomach for these trainings, and Regulus could not help but envy the ease with which he mastered everything thrown at him. Magic had always come easily to Regulus, going above and beyond the age-appropriate material with relative ease, but somehow these lessons with Bellatrix always made him feel like an incompetent, squeamish child, and he had learned quickly that to allow a trace of that on his face was met with immediate scorn and impatience.

(It was imperative that he succeed, if only to assuage whatever doubts might linger in his cousin's mind. He was not some soft child, whatever they thought.)

"We will begin with the Imperius Curse. Watch closely," Bellatrix continued, silently summoning a wire cage with two rats inside, one grey and one white. Pulling out her wand, she flourished a flick and confidently said " _Imperio_ ," the effect striking immediately as the grey rat paused its scurry across the floor of the cage. "Climb," she instructed, and the rat approached the wired walls of the cage, fit its tiny paws against the wire in a grip that seemed like it oughtn't hold, and began to climb up to the ceiling of the cage. "Let go," she said when the rat had reached the middle, and the grey rat fell to the floor again with a soft thump.

Lifting the curse, she trained her eyes on Barty first, then Regulus. "Pick a rat and practice."

Watching as the grey rat squirmed to right itself again, Regulus held his own wand at the ready and tried to replay in his mind precisely how Bellatrix had flicked her wand. Slowly he replicated the movement and looked to his cousin for confirmation. "Is the motion like that?"

"You will see when you try to cast it," she answered, her tone firm and deliberately vague. (Regulus tried not to let that tone make him nervous.) "Now command it. Extend your will."

Taking a steadying breath, Regulus flourished his wand with a quiet " _Imperio_." When the grey rat paused again, a tentative wash of relief crept over him. "Stand," he ordered simply, and the rat promptly stood, wholly obedient.

"Well done," Barty complimented with a smile settling on his face. Swiftly, he cast the spell (one wrong flourish but a prompt recovery), and his white rat was standing beside Regulus's, waiting for further instruction. "Shall they play pat-a-cake?"

"Can rats do that?" Regulus asked with his eyebrows raised.

"They can do whatever your imagination can contrive," Bellatrix answered simply.

"Then play pat-a-cake with Regulus's rat," Barty commanded without missing a beat, and when Regulus delivered the same instruction to his own, the two rats stood on their hind legs and began moving their tiny paws in time with each other, carrying out a series of motions that looked utterly ridiculous, coming from rats. (It looked ridiculous enough when it was humans) Barty's grin grew wider.

"Masterfully done, both of you," Bellatrix granted, and Regulus could feel the delight swelling in his chest at the look of clear approval on her face.

Without a doubt, this was the most successful lesson he had experienced with his cousin, and his mood brightened a little in light of such success. For an 'unforgivable' curse, the Imperius seemed versatile in its range from harmless to dangerous, based in part upon one's creativity and intent. Even with the removal of free will, 'unforgivable' sounded a bit dramatic. (Coercion took hold of free will every day, did it not?)

Regulus and Barty were releasing their hold on the rats when Bellatrix spoke again. "And now, you are to practice on each other." The two boys stared for a beat, but she did not wait for them to speak. "The will of a human is different from that of dumb animals. Human will may attempt to fight back, but your will must always be stronger. The right to control is yours to take." She was looking directly at Regulus then, pressing upon him every unspoken expectations, but it had been some time since anyone had needed to outright clarify such things. Solemnly, he nodded, and she spoke again. "You are unlikely to experience the curse as often as you will cast it, but knowing what it feels like will be beneficial for your understanding of its workings."

When Regulus looked over to Barty, his friend was already looking back at him with an expression Regulus could not quite read.

"Would you like to go first, or shall I?" Barty asked.

Suddenly, the thought of giving up control over his faculties felt a little more concerning, though Regulus knew he could not let it show on his face. (Obscuring weakness was not just for enemies, especially in the presence of Bella.) Truthfully, he did not fear Barty. If any person was to cast the curse, Regulus would prefer it be him every time, for Barty was safe and comfortable and unlikely to make a humiliating joke out of the experience, playful as he might be. Even so, he had not walked into the training session expecting to actually experience an Unforgivable.

(Regulus could not help but hope in quiet desperation that this was not to be a pattern.)

"I will," Regulus responded, holding his wand at the ready, making a conscious effort to loosen his tightened grip to emulate Bellatrix's casual stance. Meeting Barty's eyes, he cast the spell again: " _Imperio._ "

No visible change came over his friend, save for a subtle dulling of the expression, and Regulus was not quite sure what to do with him, now that the curse was cast. Pressing his lips to a thoughtful line, he scanned the room for ideas, eventually falling upon the wire rat cage again. Curiosity prickled as he flicked his gaze between Barty and the rats. "Cast the Imperius Curse on the rats." (' _Imperio_ ,' his friend said.) From the corner of his eye, Regulus could see a little smile form on his cousin's face. "Take them out and put one on each shoulder, then instruct them to stand." As Barty did so (creating yet another silly display), Regulus studied the subtleties of his friend's movements, the way they were a little smoother, almost like he was floating through the instructions, but not quite - for they were clearly purposeful movements. The rats, too, bent to Barty's will, just as Barty seemed to bend to his own.

How fascinating, the Imperius Curse.

"Put the rats back in the cage," Regulus instructed. As expected, his friend complied, and when the latch was sealed, he lifted the Imperius Curse, watching as a spark seemed to come back to Barty's eyes. Curiously, the spell on the rats seemed to lift too as they began scurrying about the cage again.

"That was...not what I expected," Barty admitted, running a hand through his hair. "Not that I want to be Imperius'd in any other situation, but that was incredibly surreal. Are you ready?"

Regulus wasn't certain he would ever be ready to be Imperius'd, strictly speaking, but he nodded nonetheless.

Barty waved his wand, and suddenly Regulus felt the most pleasant wave of relaxation wash over him like a splash of the summer sea, vague and distant as a misty morning, and all at once, he felt every responsibility and expectation tumble from his shoulders. Barty's voice was like some distant murmur, but suddenly Regulus felt like walking, and so he did - he was walking to the table and sat atop it with his legs folding up in a criss-cross. All at once, he started to feel like he did not particularly need his wand, calm as he felt upon the table, so he held it out and tossed it toward Barty, settling his hands upon his knees.

Almost as soon as the feeling had come, it faded away again, leaving him with that same intrigued feeling of tension he'd been experiencing a moment before. It was then that he truly noticed he was sitting on his cousin's mahogany table and that Barty was standing before him with both of their wands, one in each hand, and a playful smile on his face.

"Give that back," Regulus said dryly as he quickly slipped off the table again.

"I don't know what that tone is for. You're the one who gave it to me," Barty said with a wink, then tossed the wand back.

"Well done, both of you. That will be the extent of your lesson for today," Bellatrix began, and with a nod to her house-elf, the rat cage was taken away. "I expect you to continue practicing, for you never know when your victim may be adept at resistance. Rare as successful resistance might be, a poorly implemented curse makes it much easier, and you must always be the one in control." Bellatrix looked between them. "You are dismissed," she said, then turned to leave them to it, seemingly satisfied with the results.

"Do you want to practice some more?" Barty asked, a little smile still tugging at the corner of his mouth. "I wonder if we can learn to resist it."

Regulus had not particularly wanted to continue at it, yet he found himself nodding, all the same. "I wonder…"

* * *

The Cruciatus Curse was Bellatrix's favorite of the three, and her enthusiasm was evident. Learning the first of the Unforgivables had passed without a hitch, far more successfully than Regulus had anticipated, but the Cruciatus Curse was the curse of torment, and he did not feel wholly comfortable with the way his cousin's eyes glinted as she looked at the two rats between them, once again locked in their cage. She had provided her spiel, set them up for their application, yet the apprehension only pooled thicker in his stomach. (' _You must harness your aggression, tap into your_ _ **desire**_ _for the flth to suffer for their offenses_.')

Putting 'desire' and 'suffering' in the same sentiment seemed a bit much, unless it was a desire to avoid suffering, and the more she had spoken on the subject, the more he dreaded her practical application piece.

As it turned out, the anxiety was entirely justified, when at last his time came.

" _Crucio_ ," Regulus said with a sick feeling turning in his stomach, yet nothing happened. Not even a blast, not even a tiny cringe. The stupid rat just looked up at him, wriggling its nose. Apparently it had not realised he was attempting to do the same horrible thing Barty had just done to the white rat skittering in the other corner - somehow, it seemed to be the only living thing in the room that was even remotely relaxed. (The white rat's screeches were still ringing in Regulus's head… How unobservant could the creature possibly be?)

"Try again." Already, his cousin's tone was thick with impatience.

Hindsight was making it abundantly clear that letting Barty go first had been a terrible idea. Though the ordering had provided a much desired delay to his own inevitable attempts at the curse, Barty's relatively swift success made his own seem worse by comparison. It had taken a few attempts for Barty's curses to shape up to a proper Cruciatus, but at least his first had done _something_.

Frustration knotted in his chest as he flourished his wand with another _Crucio,_ this time shooting a scarlet blast that staggered the creature back, but the spell did not hold, and the animal showed no signs of greater distress. He hated that such a thing was his criteria for failure, and he gripped his wand more tightly.

"Your wandwork is perfect, but you have to mean it, Regulus," Bellatrix was saying with an edge to her tone.

" _Crucio!_ " Once again, a red blast knocked against the rat and immediately faded. Again, he attempted, then again after that with increasing agitation, and though the rat was growing increasingly jumpy from the blast, it had given little more than an occasional squeak.

"You are not even trying." Bellatrix leveled her exacting stare, and Regulus wanted to melt into the floorboards, face burning with humiliation.

"I am-" he started to object, though her chilly expression cut off the train of thought long before he got to the point that Barty, too, had required more than one attempt to hold the curse. Singling out his own struggle felt terribly unfair, but he suspected with increasing certainty that 'fairness' was not a sufficient argument.

"Again," she said sharply.

Regulus clenched his jaw, sucked in a breath, then exhaled again. " _Crucio_." A blast, once again.

"Rot it."

Startling at the difference in instruction, he looked to his cousin and saw steel in her expression. She was not the sort to lessen her demands to accommodate failure, but there was no sign of retracting the instruction as the silence buzzed between them. Turning back to the rat again, he took a steadying breath. " _Putredino_."

"The Cruciatus."

Again, his eyes flicked to her, then back to the rat. " _Crucio_."

"Slice it."

"Couldn't all of this kill it?" he asked, fighting to filter the hesitation from his voice.

"It's just a rat. We have another one. I said to slice it, Regulus," Bellatrix snipped in response with growing irritation. This time, Regulus could not quite mask the wince.

" _Diffindo._ "

"And the Cruciatus."

" _Crucio_." Like all the others, there was little more than blast, bruising the little creature at worst, and he could feel the impatience brewing within his cousin, though he could not bear to spare another glance.

Turning to Barty, Bellatrix said in razor-sharp tones, "Barty, you are dismissed for the evening."

"I don't mind staying," Barty said uncertainly, eying Regulus, though the other boy did not pull his eyes from the mess inside the rat cage.

"I would like to speak to my cousin in private," she said as her eyes, too, fell on her cousin. The air seemed to chill around them, and though Regulus could not bring himself to meet Barty's gaze, he could feel the lingering stare and saw the hesitation in his movements when at last he turned to walk out of the room. The rat was squeaking miserably now, a putrid stench thickening around them as tiny paws padded in a small pool of blood. Regulus felt his stomach roil, holding his face in a stony expression, and when the door had shut behind Barty, his cousin spoke again, "We are going to keep doing this until you understand. You are a Black, fully capable of a curse of this magnitude, and I will not have my own cousin consider the comforts of vermin over the progression of his magical repertoire or the responsibilities of his position in this organisation."

"I'm not-"

"Cast the curse correctly, Regulus," she interrupted cooly.

The rats were both squeaking now, one zipping in short jagged bursts while the other squirmed to try and tend to its lacerations and the rotted patch oozing from its side. Regulus hardened his stance to stone. The rat's suffering would only compile, the longer Regulus failed. (As would his own, however different that suffering might be.) Hesitation would do neither of them any more favors.

Perhaps sometimes, pain was the only way to end pain.

" _Crucio!_!" he said sharply, and immediately the rat's screeching rocketed, writhing against the floor of the cage as its fur smeared red. The curse held for only a few seconds, but even as it lifted, Regulus could hear the rat's shrill shriek. (Was it real or an echo in his head? He could not tell.)

"See? I knew you were capable," Bellatrix said, gesturing towards him with her hand. Though some degree of impatience remained in her tone, the the intensity had calmed once again as a hint of leniency returned to her demeanor. "That was well done. You may counter-curse and mend the creature if you so desire, but you are dismissed for the evening."

Numbly, Regulus nodded, tightening his throat to fight the rising bile as his eyes lingered on the matted fur. Quietly, he reversed the creeping rot and cast a mending spell for the wounds, but the bloodied image lingered behind his eyes, even as he turned to walk out of the room, out of the manor, down into the snow. He had barely reached the bottom of the steps when he felt his stomach rebel, lurching up his throat as he fell to a crouch next to the nearest bush. Fighting against the rush of bile, he clenched his eyes closed with a wince and leaned back against the outer railing of the steps.

"It's done," he whispered to himself, curling his knees up against his chest and looking up to the devastatingly clear sky. _That was well done_. (Don't think, don't think, everything is fine, don't think about it.) In his mind, the rat slipped in a pool of scarlet. _It's just a rat._ "It's just a rat." (The stars were so bright tonight, gleaming bright and white as the blanket of snow around him.)

The sky had been cloudier, three nights before when the vigilantes crashed the Death Eater's most recent meeting. Unbidden, Regulus thought of his brother, then, face flushed with the chill of snow and the heat of anger. _'Monster,'_ Sirius had called him. His comrades had been preoccupied with where the leak in information had occurred, but all Regulus cared about was the horror and disgust in his brother's eyes when that bone-white mask had dropped between them.

"I'm not a monster," he whispered to the stars. (Breathe in, breathe out.)

Regulus could not say how long he had sat in this snow, winter air biting at his ears and his nose and seeping into his clothes, but as he stood, he could feel the weight of his cloak, soaked all along the bottom, and every breath burned icily against the cold. In the stillness, his mind calmed, red washing to a stretching scene of black and white.

He would do what needed to be done. Anything less would always make it worse.

It was the stars he thought about as he apparated home, the stars and the nipping wind and the way the snow dusted on the trees. Perhaps someday, it would get easier.

* * *

The winter winds sounded strange, whipping just outside the cove where Regulus and Barty had tucked away with their books and their warming spells. It was barren here at Porth Iago - no one wanted to visit in the winter when the waters were murderously chilly, but it was the solitude, more so than the waters, that drew them in.

"We have one more," Barty said quietly. "Let's learn it together. Here. Right now."

Subtly, Regulus tipped his head toward his friend. "She hasn't told us we need to do that one yet." There was an anxious edge to his voice that he hated, but it could not be helped, now. Several days had passed since their last lesson - several days of aggressive forgetting - and now that his mind had fully settled again, he was not keen to send it reeling.

"Bellatrix is going to make you nervous again." Regulus was opening his mouth to say something, but Barty cut him off at once, "Don't get me wrong, your cousin is incredibly effective, but do you really want have her critiquing your first attempt on this one?"

Miserably, Regulus rested his head back against the weathered stone of their tucked away cove, watching the tide as it rolled over the sand. "You don't think I can do it."

"I don't think you want to do it."

"I'm not a-" _(_ _ **traitor**_ _)_

"-I know you're not," Barty interrupted. "You're brilliant and devoted with unquestionable loyalty, and your family should count themselves lucky to have you. That's not what I meant."

The earnestness in his friend's voice was staggering, and Regulus could feel his face heating against the cool, salty breeze. "Yes, well, you're pretty brilliant, yourself. A natural. Not just in this, but everything. Half the time, I'm pretty sure she would prefer to be related to you, following these trainings."

"I won't deny I'm brilliant," Barty said with the flash of a wicked grin, still lingering at the corners of his mouth as his eyes traced the line of Regulus's profile, "We're both brilliant. She's hard on you because she knows you're capable of so much more. You've got a block in your mind, a wall we've got to tear down," he said, reaching up to press his thumbs to Regulus's temples, as if to cave in some unseen barrier, and angling his friend's gaze to meet his own. "I'm going to help you."

Regulus felt a twist in his chest, a strange flip; he couldn't quite tell if it was anxiety or affection or some muddled mix of both, but he relaxed against the pressing fingers and nodded as the sound of waves crashed against sand and stone.

When Barty retracted his hands and stood to approach a nearby patch of grass, Regulus could feel chilly air creeping over the warm, finger-small patches of his temple. The beauty of the Welsh seaside beckoned, painting the water in evening colors, but for a moment, his eyes were fixed on the line of his friend's frame, bundled in robes and a Slytherin scarf to match Regulus's own. The straw-blond mop of hair looked almost red, cast against the setting sun.

(Red, like-)

As Barty turned back again and caught his eyes full on, Regulus fought the urge to divert his gaze and pretend he'd been staring at the stone wall, but with some level of embarrassment, he reminded himself that it was not a crime to look at people, even if it felt a little bit like one to be caught, sometimes. Barty just smiled, and with a flick of his wand, floated a rather large beetle in front of him for his return. Just a pace shy of Regulus, Barty lowered the bug to the ground again and transfigured the sandy surface into a glass box that enclosed the scurrying beetle.

Regulus knew what was coming next, and he hated the familiar dread settling in his stomach.

"This one isn't about passion so much as resolution," Barty reminded him in hushed tones, shifting to stand behind his friend, "and a willingness to eliminate that which stands between you and your goal."

 _Control. Torment. Elimination._ Bellatrix's voice echoed in his mind, and Regulus nodded, reaching into his pocket to pull out his own wand, thumb securing a steady grip. ('Resolution,' Barty had said, and Regulus found that he liked that better. 'Resolution.') Pointing at the scuffling beetle and clamping his eyes shut, Regulus could feel his heartbeat thumping in his head. Quietly, he said, " _Avada Kedavra._ "

Nothing happened.

Once again, Regulus could not quite tease apart whether that rush of emotion was misery or relief.

"It's a meaningless bug," Barty coached, and Regulus pressed his lips to a line. "You don't have to subjugate it. You just have to crush it, like you would any bug beneath your shoe."

(Crush it, like a bug. Regulus did not particularly want to step on any bugs, either, but somehow he suspected such an argument was missing the point.)

Sucking in the cold, salty breeze, Regulus leveled his wand again and looked at the beetle. There was nothing particularly remarkable about the creature: Accomplishing nothing, understanding nothing. The Killing Curse was a willingness to snuff out a life, to cut away what was undesired or unnecessary. Regulus did not want to kill the beetle for killing's sake - there was no purpose in it, no Cause - but despite Barty's proximity, it was his cousin's eyes that he felt boring into the back of his head.

(The Cruciatus was ending pain with pain. Perhaps the Killing Curse was a willingness to put your own desires second, in a similar sense. To do what needed to be done.)

He would do what needed to be done, or it would only get worse.

Rubbing his thumb along a worn groove of his wand, Regulus watched the beetle scuttle around in its glass cage for a beat longer before he said with quiet clarity, " _Avada Kedavra._ "

It was the sudden stillness, more so than the subtle collapse, that told of the curse's success.

"You did it!" Barty whispered with a smile in his voice, leaning in to peer over Regulus's shoulder. "And on the second try, no less."

Regulus's eyes were fixed on the beetle. The glass cage was reduced back to sand, sprinkling on and around its lifeless carcass like some half-baked play at a burial. It felt wrong, the way the spindly legs curled in on themselves. Bugs were squashed from existence on a regular basis, both with purpose and without, so why did this feel so different?

"You are certain to impress Bellatrix when this one comes up," Barty was continuing, hands clasping his shoulders from the back and shifting to catch his eyes.

Regulus read the call for acknowledgement and turned his head to return the look. A certain intensity coloured his friend's expression, searching and waiting for an extension on return. Regulus knew the look well - and wore it well, too, for in that ache for acceptance, they had always been kindred spirits. Carefully, he constructed a smile on his face. (Barty had helped him avoid further humiliation with Bella - that, at least, was something to smile about.)

"I could not have done it without you," Regulus said, pouring affection into those hollow gaps left behind by the harrowing green flash.

The way Barty's face lit up was well worth it. "You would have figured it out eventually," Barty said, though he was clearly preening. "But that was pretty fast, wasn't it? I should become a professor."

"Come along, then, Professor Crouch," Regulus said mildly as Barty retracted his hands to rub them together. With a little flick of his wand, Regulus cast fresh warming spells on each of their hands and cloaks in turn, then stuck his wand back in his pocket, scrubbing the image of the beetle from his mind. "We should get supper before heading back."

"Supper is an excellent plan. Professor, though. I like it. Feel free to keep calling me that," Barty said with a grin as they started walking out from the sheltered cove.

Regulus snorted softly, shaking his head. "I most certainly will not."

With a crack, the two boys disappeared from the beach; in the cove, a howling gust swept a blanket of sand over the lifeless beetle.


End file.
